Photocatalytic Activity of TiO2-Doped Fe, Ag and Ni with N under Visible Light Irradiation

Doping with noble metal ions or doping with nitrogen has been attempted to prepare TiO2 that reacts even in visible light. In this study, TiO2 was doped with nitrogen and various metal ions instead of noble metals. The TiO2 photocatalysts doped with metal ions (Fe, Ag, Ni) and nitrogen were prepared by a sol-gel method. Their physicochemical properties were characterized and their photocatalytic activities were investigated under visible light irradiation. In TiO2 doped with metal ions and nitrogen, the light absorption region was extended to visible light. The photoluminescence intensity was much greater in N/Ni/TiO2 than in N/Ag/TiO2 and N/Fe/TiO2. The photolysis activities of N/Ni/TiO2 were the highest in formaldehyde decomposition and methylene blue decomposition. The sterilization efficiency of N/Ni/TiO2 was the highest in the evaluation test for the inhibition of the proliferation of Pseudomonas aeruginosa. The bandgap of N/Ni/TiO2 was 2.4 eV, which was significantly lower than that of anatase TiO2 (3.2 eV). The N/Ni/TiO2 had a much higher optical intensity than other metal ion-doped TiO2, so it was highly active under visible light irradiation.

Real-Time Monitoring of Doxorubicin Release from Hybrid Nanoporous Anodic Alumina Structures

This work demonstrates an advanced approach to fabricate Hybrid nanoporous anodic alumina gradient-index filters (Hy-NAA-GIFs) through a heterogeneous anodization process combining sinusoidal current-density anodization and constant potential anodization. As a result, the hybrid structure obtained reveals a single photonic stopband (PSB), which falls within the absorption region of the drug molecule and the intensity of the spectrum that are far from such absorption range. The prepared structures were loaded with the doxorubicin (DOX) drug through the drop-casting method, which allows for evaluating the maximum reflectance of the relative height of the PSB with the average reflectance of the spectrum intensity. Thereafter, this property has been applied in a flow cell setup connected to a reflectance spectrophotometer where different drug-loaded samples were placed to study the behavior and kinetics of the drug release in real-time by varying two parameters, i.e., different pore length and flow rates. As such, obtained results were analyzed with a model that includes a sum of two inverted exponential decay functions with two different characteristic time releases. Overall, this study opens up several possibilities for the Hy-NAA-GIFs to study the drug kinetics from nanoporous structures.

Study of the parameters of molybdenum oxide films by optical methods

In this work, the physical properties of molybdenum oxide films obtained by reactive magnetron sputtering were studied. Based on the experimental transmission and reflection spectra for samples at different currents in the fundamental absorption region, the optical band gap was determined, and in the visible range, the thickness of the films was defined. The studied films had the values of optical parameters that were observed by other authors. However, the dependence of the optical band gap width on the thickness of the films is not found in the literature and can be associated with the influence of the flux density of the substance sputtered from the target surface on the structure of the film.

Design and Fabrication of a Low-Cost Thermopile Infrared Detector

In this paper, we design and optimize a low-cost, closed-film structure of a microelectromechanical systems (MEMS) thermopile infrared detector. By optimizing the circular arrangement of thermocouple strips and the thermal isolation design of the cold end to pursue a higher temperature difference, in addition to eliminating the absorption region, silicon nitride is deposited on the whole device surface as a passivated absorption layer. This reduces the cost while maintaining the voltage response and is suitable for mass production. The optimized detector had a 22.6% improvement in the response rate to 34.2 V/W, a detection rate of 1.02 × 108 cm·Hz1/2/W, and a response time of 26.9 ms. The design optimization of this detector provides a reference for further development of IR detectors.

Tungsten Based Spectrally Selective Absorbers with Anisotropic Rough Surface Texture

Spectrally selective absorbers have received considerable interest due to their applications in thermophotovoltaic devices and as solar absorbers. Due to extreme operating conditions in these applications, such as high temperatures, thermo-mechanically stable and broadband spectrally selective absorbers are of interest. This paper demonstrates anisotropic random rough surfaces that provide broadband spectrally selective absorption for the thermo-mechanically stable Tungsten surfaces. Anisotropic random rough surface has different correlation lengths in the x- and y-directions, which means their topography parameters have directional dependence. In particular, we demonstrate that spectral absorptance of Tungsten random rough surfaces at visible (VIS) and near-infrared (NIR) spectral regions are sensitive to correlation length and RMS height variations. Our results indicate that by optimizing random rough surface parameters, absorption values exceeding 95% can be obtained. Moreover, our results indicate that anisotropic random rough surfaces broaden the bandwidth of the high absorption region. It is shown that in VIS and NIR regions, the absorption enhancements of up to 47% and 52% are achieved for the isotropic and anisotropic rough surfaces, respectively.

Novel Field Effect Photodiode to Control the Output Photocurrent and Fast Optical Switching

This paper presents a novel device named Field Effect Photodiode (FEPD) to overcome the inherent drawbacks of PIN Photodiode (PIN-PD) and having an accurate control of the output photocurrent either applying the regular PIN-PD as a fast optical switch that provides a desire I ON /I OFF ratio for optical applications in the nanoscale regime. The proposed device combines a Metal Semiconductor Field Effect Transistor (MESFET) and a regular PIN-PD device that can convert the incident light with photon energy greater than the semiconductor’s bandgap to the regulated photocurrent by changing the gates bias which mounted over the absorption region. Our work include additional models such as bandgap narrowing, Shockley–Read–Hall (SRH), Auger (AUGER), the dependence of the carrier mobility on the doping concentration, Lombardi mobility model (CVT), Fermi statistic dependence (FERMIDIRAC), and Lateral electric field-dependent mobility. To extract and illustrate the electrical and optical results of both the regular PIN-PD and the proposed FEPD in this work, we have used TCAD tools as a semiconductor simulator.

Synthesis of n-Alkoxy Derivatives of Layered Perovskite-Like Niobate HCa2Nb3O10 and Study of Their Photocatalytic Activity for Hydrogen Production from an Aqueous Solution of Methanol

A series of hybrid inorganic–organic niobates HCa2Nb3O10×ROH, containing n-alkoxy groups of primary alcohols (R = Me, Et, Pr, Bu, Hx, and Dc) grafted in the interlayer space, has been studied for the first time in relation to photocatalytic hydrogen generation from a model 1 mol % aqueous solution of methanol under ultraviolet irradiation. Photocatalytic activity was measured both for bare samples and for their composites with Pt nanoparticles as a cocatalyst. The advanced measurement scheme allowed monitoring the volume concentration of a sample in a suspension during the experiment, its pH, and possible exfoliation of layered compounds into nanolayers. In the series of n-alkoxy derivatives, the maximum rate of hydrogen evolution was achieved over a Pt-loaded ethoxy derivative HCa2Nb3O10×EtOH/Pt. Its apparent quantum efficiency of 20.6% in the 220–350 nm range was found not to be caused by changes in the light absorption region or specific surface area upon ethanol grafting. Moreover, the amounts of hydrogen released during the measurements significantly exceeded those of interlayer organic components, indicating that hydrogen is generated from the reaction solution rather than from the hybrid material.

Comparative Study of Si-Ge-Sn Resonant Cavity Enhanced Heterojunction Bipolar Phototransistor (RCE-HPT) under Quantum Confined Stark Effect (QCSE) and Franz Keldysh Effect (FKE) at 1.55 µm

Group-IV and their alloy based Heterojunction Bipolar Phototransistors (HPTs) are of immense interest in recent day optical communication. In this paper first resonant cavity enhanced heterojunction bipolar phototransistor (RCE-HPT) with Ge0.992Sn0.008/Si0.30Ge0.61Sn0.09 Quantum Well/barrier structure under Quantum Confined Stark Effect (QCSE) has been evaluated. Further the bulk GeSn absorption region has been considered instead of QW/barrier structure and estimated the Franz Keldysh Effect (FKE). Finally different RCE-HPT related parameters such as quantum efficiency-bandwidth product, responsivity, collector current and optical gain have been studied and compared under QCSE and FKE.

Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors

Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic photodetectors have been shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband devices. Here, we demonstrate fully vacuum-processed narrow- and broadband photomultiplication-type organic photodetectors. Devices are based on enhanced hole injection leading to a maximum external quantum efficiency of almost 2000% at −10 V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer state absorption region. By making use of an optical cavity device architecture, we enhance the charge-transfer response and demonstrate a wavelength tunable narrowband photomultiplication-type organic photodetector with external quantum efficiencies superior to those of pin-devices. The presented concept can further improve the performance of photodetectors based on the absorption of charge-transfer states, which were so far limited by the low external quantum efficiency provided by these devices.

Solution Processed Zn1−x−ySmxCuyO Nanorod Arrays for Dye Sensitized Solar Cells

Cu- and Sm-doped ZnO nanorod arrays were grown with 1 wt% of Sm and different weight percents (0.0, 0.5, 1.0 and 1.5 wt%) of Cu by two-step hydrothermal method. The influence of Cu concentration and precursor of Sm on the structural, optical and photovoltaic properties of ZnO nanorod arrays was investigated. An X-ray diffraction study showed that the nanorod arrays grown along the (002) plane, i.e., c-axis, had hexagonal wurtzite crystal structure. The lattice strain is present in all samples and shows an increasing trend with Cu/Sm concentration. Field emission scanning electron microscopy was used to investigate the morphology and the nanorod arrays grown vertically on the FTO substrates. The diameter of nanorod arrays ranged from 68 nm to 137 nm and was found highly dependent on Cu concentration and Sm precursor while the density of nanorod arrays almost remains the same. The grown nanorod arrays served as photoelectrodes for fabricating dye-sensitized solar cells (DSSCs). The overall light to electricity conversion efficiency ranged from 1.74% (sample S1, doped with 1 wt% of Sm and 0.0 wt% of Cu) to more than 4.14% (sample S4, doped with 1 wt% of Sm and 1.5 wt% of Cu), which is 60% higher than former sample S1. The increment in DSSCs efficiency is attributed either because of the doping of Sm3+ ions which increase the absorption region of light spectrum by up/down conversion or the doping of Cu ions which decrease the recombination and backward transfer of photo-generated electrons and increase the electron transport mobility. This work indicates that the coupled use of Cu and Sm in ZnO nanorod array films have the potential to enhance the performance of dye-sensitized solar cells.